A 30-year-old man had a "flu-like" syndrome followed by clinical and laboratory evidence of myositis localized in both thighs. Serum neutralization test results were compatible with enterovirus echo 9 infection. Severe myoglobinuria dominated the clinical picture. We discuss other possible manifestations of enterovirus echo 9 infections. To our knowledge, this report is the first describing myositis caused by enterovirus echo 9.